SYPHILIS. 315 



through the flame, are kept for from twelve to twenty-four hours 

 at room-temperature and then in a solution of aniline- water gen- 

 tian-violet for two hours more at a temperature of 40 C. (104 

 F. ) . They are next decolorized in absolute alcohol, and are then 

 exposed for ten seconds to the action of i^ per cent, aqueous 

 solution of potassium permanganate, from which they are trans- 

 ferred to an aqueous solution of chemically pure sulphurous acid. 

 They are then washed in water and again immersed in the po- 

 tassium-permanganate solution, but now only for three or four 

 seconds, and from this they are transferred to the solution of 

 sulphurous acid ; and this is repeated until the preparation ap- 

 pears entirely decolorized, which usually is brought about after 

 the manipulations have been repeated three or four times. The 



Fig. 69. Bacillus of syphilis (Lustgarten), from a condyloma; X 1000 (Itzerott and 



Niemann). 



preparations are then dehydrated in alcohol, cleared in oil of 

 cloves, and mounted in xylol Canada balsam. 



Lustgarten believed that by this method of decolorization all 

 bacteria but the syphilis-bacilli, the tubercle-bacilli, and the 

 leprosy-bacilli yield up their stain. The last two, however, are 

 distinguished by their resistance to hydrochloric acid and nitric 

 acid, both of which rapidly decolorize the syphilis-bacilli. 

 Lustgarten found the bacilli stained in this way in all syphilitic 

 infiltrates, and in smaller number at the center and in larger 

 number at the periphery, as well as in the adjacent apparently 

 healthy tissues. They rarely lie free, but singly or in groups of 

 from two to nine within large lymphoid cells. On one occasion 

 Lustgarten encountered them in the lumen of a large lymphatic. 



